A 48–80-V Input 2-MHz Adaptive ZVT-Assisted Bus Converter With Light-Load Efficiency Improvement

This article presents a dc–dc bus converter with a new soft-switching scheme. Adaptive zero-voltage transition (AZVT) is proposed to enable ZVS turn-on of the power FET via a ZVT auxiliary branch for removing the switching loss of the converter. In AZVT, the current of the auxiliary branch is discontinuous and its peak value is controlled to decrease with the load current. This feature not only minimizes the conduction loss of the auxiliary branch but also significantly improves the light-load power efficiency of the converter. In addition, a high-voltage flipped current sensor (HVFCS) is developed to enable fast and accurate auxiliary inductor current sensing for supporting proper AZVT control in the MHz range. The proposed converter was validated using three 100-V e-mode GaN FETs together with the proposed AZVT controller and gate drivers implemented in a 0.5- $\mu \text{m}$ , 120-V CMOS process. The proposed AZVT converter supports a wide input range from 48 to 80 V, operates at 2 MHz, and provides the power efficiency improvements up to 14.5% and 8.7% over the hard-switching operation at the input voltages of 48 and 80 V, respectively. Compared with the state-of-the-art designs, the proposed converter not only obtains >90% power efficiency over a load range of 6–60 W but also improves light-load efficiency by over 5% with more than two times higher switching frequency.